A rack and pinion is a type of linear actuator that comprises a pair of teethed members which convert rotational motion into linear motion. A circular teethed member, i.e. a gear wheel called “the pinion”, engages the teeth of a linear bar called “the rack”. Rotational motion applied to the pinion causes the rack to move relative to the pinion, thereby translating the rotational motion of the pinion into linear motion. Rack and pinion combinations are often used as part of a simple linear actuator in a drill stand, for example, where the rotation of a shaft powered by hand or by a motor is converted to linear motion.
U.S. Pat. No. 6,692,201 B2 (Soderman) discloses a portable drill press that has a rack bar with a brace attached at one end. A pinion slide assembly is slideably engaged with the rack bar such that the pinion is in rotational engagement with a rack. The pinion slide assembly may be retained on the rack bar by a bolt. The pinion may be attached to a pinion shaft that may be rotated by a rotation lever. Thus, the pinion shaft is the input shaft and the design is too simple to be called a gearbox. A mounting bracket may be attached to the pinion slide assembly for attachment of a hand drill.
DE 37 24 232 C2 (Fein GmbH & Co.) discloses a drill stand with a base part comprising a foot, in particular an adhesive foot, as well as a machine slide which is displaceably mounted on the base part and is traversable relative to the base part by an adjusting device which can be driven by a rotatable manual actuating device. Thus, the pinion is fixed to the input shaft and the design is too simple to be called a gearbox. In order to improve the drill stand in such a way that detachment of the foot from the bearing surface can be avoided, it is proposed that the manual actuating device that rotates the input shaft have a drive torque limiter.
DE 34 08 457 A1 (Podobnik) relates to an upright for basic core-drilling tools, in particular for the working of concrete, consisting of a base plate with column and slide guide for accommodating the drive motor with drilling spindle, in which the column is equipped with a milled-in and welded toothed rack and a locking groove, and the slide running on the column is equipped with a roller guide with eight rollers or shafts running on the sides of the column, and the rollers and shafts run on the sides of the column without play. The advantages of the device according to the invention are that a good cutting capacity of the drill bit is achieved and exact spot drilling is obtained through precise guidance of the drilling tool. Also in this case, the pinion is fixed to the input shaft and the design is too simple to be called a gearbox.
U.S. Pat. No. 2,995,960 (Riley, Jr., et al.) relates to a shiftable two-speed feeding and retracting means for a power-operated tool, and more particularly, to such means which is associated with a drill stand having a supporting column and further having a drill carriage including a power-operated drill positioned upon said column. The two-speed gearbox is complicated and comprises an axially displaceable input shaft, an intermediate shaft and a transverse shaft. Further, it comprises two gear wheels that are axially movable on the input shaft and selectively lockable thereto, two gear wheels and a worm fixed to the auxiliary shaft, and a worm wheel and a pinion fixed to the transverse shaft.
DE 10 2011 122 028 A1 (Kastner) relates to a drill stand has a rack gear portion that is secured at a guide column portion. An auxiliary gear box is connected with a speed reduction gear element for reducing the speed of a feed mechanism. The speed reduction gear element is provided with a drive shaft and a driven shaft. The rotating movement of a rotary drive unit is transferred on a rack gear intervention gear wheel through the auxiliary gear box or without the auxiliary gear box. Also here, the gearbox is unnecessarily complicated. Even though it is a single speed gearbox, it comprises an input shaft, an intermediate shaft and a transverse shaft, and further a gear fixed on the input shaft, a gear and a worm fixed on the intermediate shaft, and a worm wheel and a pinion fixed on the transverse shaft.
U.S. Pat. No. 8,888,417 B2 (Jonsson, et al.) is assigned to the assignee of the present application and relates to methods and systems for automatically feeding a feeding housing of a drilling device. The drilling device includes a drill stand, a drilling machine and a feeding housing. Further, the drilling machine, which is suspended by the feeding housing, includes a drill with a drilling motor for performing a drilling operation through a drilling object. The feeding unit includes an electric feeding motor for feeding the feeding housing along the stand. Further, the feeding unit also includes a controller for manually influencing the feeding motor's direction of rotation, speed and feeding force. No description of a gearbox is included.
The gearbox of the present invention can be applied in the system of the '417 patent but can, of course, be applied also in drill stands of the types referred to above and also in other rack and pinion applications.
In all drill stands of the types referred to above, the teeth of the rack and pinion transmission will be exposed to high levels of stress, especially in cases where the drill gets stuck during drilling, and the operator tries to make it come loose again.